CN101073171B - Deposition of LiCoO2 - Google Patents

Abstract

According to the present invention, deposition of LiCoO by pulsed dc physical vapor deposition is described₂And (3) a layer. Such deposition can provide LiCoO₂Low temperature, high deposition rate deposition of crystalline layers, said LiCoO₂The crystalline layer is desirably<101>Or<003>And (4) orientation. Some embodiments of the deposition address LiCoO₂The need for high rate deposition of films, the LiCoO₂The film may be used as a cathode layer in a solid-state rechargeable Li battery. Embodiments of the method according to the present invention can eliminate the conventional practice of making the LiCoO₂High temperature required for layer crystallization (>700 deg.C) annealing step.

Description

Deposition of LiCoO2

related application

This application claims priority to the following provisional applications: provisional application 60/651,363, filed February 8, 2005, by Hongmei Zhang and Richard E. Demaray; and provisional application 60/60, filed December 8, 2004 by the same inventor 634,818, each provisional application is hereby incorporated by reference in its entirety.

Background of the invention

technical field

The present invention relates to thin-film solid-state batteries and, in particular, to the deposition of _LiCoO2 films and layers for battery fabrication.

Discussion of related technologies

Solid-state thin-film batteries are typically formed by laminating thin films on a substrate such that the films cooperate to generate a voltage. The thin film typically contains a collector, cathode, anode and electrolyte. The films can be deposited using a variety of deposition methods including sputtering and electroplating. Substrates suitable for this application are conventionally high temperature materials capable of undergoing at least one high temperature annealing treatment of at least 700 °C in air for up to about 2 hours to crystallize the _LiCoO2 film. Such a substrate may be any suitable material with suitable structural and material properties, such as a semiconductor wafer, a metal sheet (such as titanium or zirconium), a ceramic such as alumina or other material subjected to a subsequent high temperature treatment in the presence of _LiCoO , The _LiCoO2 can undergo significant interfacial reactions with most materials used in batteries during these temperature cycles.

Other lithium-containing mixed metal oxides besides _LiCoO2 have been evaluated as crystalline energy storage cathode materials, containing Ni, Nb, Mn, V and sometimes Co, but also other transition metal oxides. Typically, the cathode material is deposited in an amorphous form and then heated in an annealing process to form a crystalline material. In _LiCoO2 , for example, annealing above 700 °C transforms the deposited amorphous film into a crystalline state. However, such high-temperature annealing severely limits the materials that can be used as substrates, induces destructive reactions with lithium-containing cathode materials, and often requires the use of expensive noble metals such as gold. These high thermal budget approaches (ie, high temperatures for long periods of time) are incompatible with semiconductor or MEM device processing and limit the choice of substrate materials, increasing cost and reducing the yield of these cells.

It is known that the crystallization of amorphous _LiCoO2 on noble metals can be achieved. An example of such crystallization is discussed in Kim et al., where a conventional furnace annealing of an amorphous layer of _LiCoO2 on a noble metal at 700 °C for 20 min achieved crystallization of the _LiCoO2 material as shown by x-ray diffraction data. Kim, Han-Ki and Yoon, Young Soo, "Characteristics of rapid-thermal-annealed LiCoO ₂ , cathode film for an all-solid-state thin film microbattery," J.Vac.Sci.Techn.A22(4), 2004 July/August. In Kim et al., a _LiCoO2 film was deposited on a platinum film deposited on a high temperature MgO/Si substrate. It was shown in Kim et al. that these crystalline films are capable of constituting the Li ⁺ ion-containing cathode layer of a functional all-solid-state Li ⁺ ion battery.

There are many references disclosing an ion beam assisted method capable of providing _LiCoO2 films showing some _observable crystalline composition by small angle x-ray diffraction (XRD). Some examples of these films are found in US Patent Application Serial Nos. 09/815,983 (Publication No. US2002/001747), 09/815,621 (Publication No. US2001/0032666), and 09/815,919 (Publication No. US2002/0001746). These references disclose the use of a second frontside ion beam or other ion source in parallel with the deposition source to obtain an overlapping region of ion flux and _LiCoO2 vapor flux at the substrate surface. None of these references disclose film temperature data during deposition or other temperature data of the film to support claims of low temperature processing.

It is difficult to form a uniform deposition by sputtering a layer of material or by bombardment using ion flux. Using two uniform simultaneous distributions from two sources occupying different positions and extents relative to the substrate greatly increases the difficulties involved in achieving uniform material deposition. These references do not disclose the uniform material deposition required for reliable fabrication of thin film batteries. One-sigma material uniformity of 5% is a standard in thin-film production. About 86% of the films with this uniformity were found to be acceptable for cell fabrication.

It is also more difficult to manufacture dimensions such as 200mm or 300mm in substrate scale. Indeed, in the above discussed references using sputter deposition as well as ion beam deposition, only small area targets and small area substrates are disclosed. These references disclose only feasibility results. A method of achieving uniform distribution from two independent front side sources is not disclosed in these references.

Additionally, conventional materials and fabrication methods can limit the energy density capabilities of manufactured batteries, resulting in more batteries needing to occupy more volume. There is a particular need to manufacture batteries with large energy storage per unit volume to provide batteries of low weight and volume.

Therefore, there is a need for low-temperature methods for depositing crystalline materials such as _LiCoO2 materials onto substrates. In particular, methods are needed that allow the fabrication of anode lithium films for battery structures with a sufficiently low thermal budget to allow fabrication of functionalized structures on low temperature materials such as stainless steel, aluminum or copper foil.

Summary of the invention

According to the present invention, the deposition of _LiCoO2 layers by pulsed DC physical vapor deposition is described. This deposition can provide low temperature, high deposition rate deposition of _LiCoO2 crystalline layer with suitable <101> orientation. Some embodiments of the deposition address the need for high rate deposition of _LiCoO2 films that can be used as _cathode layers in solid-state rechargeable Li batteries. Embodiments of the method according to the invention can eliminate the high temperature (>700 °C) annealing step conventionally required to crystallize LiCoO _layers .

A method of depositing a _LiCoO layer according to some embodiments of the invention includes placing a substrate in a reactor; flowing a gas mixture comprising argon and oxygen through the reactor; and applying pulsed DC power to the relative The above substrate was placed on a target formed of LiCoO ₂ . In some embodiments, a _LiCoO2 layer is formed on the substrate. Furthermore, in some embodiments, the _LiCoO2 layer is a crystalline layer of orientation <101>.

In some embodiments, stacked battery structures can be formed. The stacked battery structure comprises one or more battery stacks deposited on a thin substrate, wherein each battery stack comprises: a conductive layer, a crystalline LiCoO layer deposited on the conductive layer, _a layer of crystalline LiCoO deposited on the a LiPON layer on the _LiCoO layer; and an anode deposited on the LiPON layer. A top conductive layer may be deposited on the one or more battery stacks.

In some embodiments, cell structures can be formed in a cluster tool. A method of manufacturing a battery in a cluster facility comprising: loading a substrate into the cluster facility; depositing a conductive layer on the substrate in a first chamber of the cluster facility; In the second chamber of the agglomeration device, a layer of crystalline _LiCoO2 is deposited on the conductive layer; in the third chamber of the aggregation-type device, a layer of LiPON is deposited on the _LiCoO2 layer; in the fourth chamber, a layer of an anode layer is deposited on the _LiCoO layer; and in the fifth chamber of the concentration device, a second conductive layer is deposited on the LiPON layer.

The fixing means for fixing the thin substrate may comprise a top and a bottom, wherein the thin substrate is fixed when the top is attached to the bottom.

These and other embodiments of the invention are further discussed below with reference to the following figures. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. Furthermore, specific statements or theories regarding the deposition or performance of certain layers during the deposition process or in the operation of devices incorporating these layers are presented for illustration only and should not be considered limiting of the present disclosure or rights. required range.

Brief description of the drawings

Figures 1A and 1B illustrate a pulsed DC biased reactive deposition apparatus that can be used in the deposition method according to the present invention.

Figure 2 shows an example of a target that may be used in the reactor illustrated in Figures 1A and 1B.

Figure 3 illustrates a thin film battery design according to some embodiments of the invention.

Figures 4A and 4B show x-ray diffraction analysis and SEM photographs of _LiCoO2 films deposited according to embodiments of the present invention.

5A to 5E show SEM photographs of _LiCoO2 films according to some embodiments of the present invention.

Figure 6A illustrates a _LiCoO2 layer deposited on a thin substrate according to some embodiments of the present invention.

Figure 6B illustrates a _LiCoO2 layer deposited over a conductive layer on a thin substrate according to some embodiments of the invention.

Figures 7A, 7B, 7C, and 7D illustrate configurations of thin substrate holders and masks that may be used in the deposition of _LiCoO2 layers deposited according to some embodiments of the present invention.

Figure 8 illustrates an aggregated device that can be used to form cells with a _LiCoO2 layer deposited according to some embodiments of the present invention.

Figures 9A and 9B illustrate examples of stacked cell structures with _LiCoO2 layers deposited according to some embodiments of the present invention.

10A to 10D illustrate the steps of deposition and annealing of _LiCoO2 deposited on top of an iridium layer on a silicon wafer.

11A through 11D illustrate a single layer cell formed on top of an iridium layer according to some embodiments of the invention.

12A to 12L illustrate the deposition of crystalline LiCoO _layers on silicon or alumina substrates.

In the figures, elements with the same label have the same or similar functions.

Detailed description of the invention

According to an embodiment of the present invention, a _LiCoO2 film is deposited on a substrate by a pulsed dc physical vapor deposition (PVD) method. In contrast to, for example, Kim et al., _LiCoO2 films according to some embodiments of the present invention provide crystalline _LiCoO2 films that are deposited at substrate temperatures as low as about 220°C on the substrate. An as-deposited LiCoO ₂ film can be easily matured to a highly crystalline state by annealing. In addition, when disposed on a noble metal film, the as-deposited crystalline film can be annealed at a further greatly reduced temperature, for example as low as 400 to 500°C instead of at 700°C, thus providing a lower temperature substrate for solid-state batteries. Deposition, annealing and fabrication on substrates.

In this application, a single extended source is described that does not require a second front side ion source or ion assistance, the single extended source scaled to 400mm x 500mm for fabrication to an area of ^2000cm2 A 1-sigma with _a LiCoO uniformity of 3% measured at 25 points was achieved at a deposition rate of 1.2 μm thickness per hour.

Regarding other depositions using this method, temperature measurements of the substrate during deposition indicated that the substrate remained less than 224°C. Temperature measurements were made using a temperature sticker (Model no. TL-F-390, active at 199-224°C) purchased from Omega Engineering, Stamford, Ct.

Furthermore, in some embodiments, films deposited according to the present invention can have deposition rates that are about 10 to about 30 times higher than conventional film methods. In Table I are illustrated the deposition thicknesses and deposition times for films deposited according to the invention. Furthermore, films according to the invention can be deposited on wide-area substrates having a surface area 10 to 50 times that of existing sputtering methods, resulting in much higher productivity and Much lower manufacturing costs, thereby providing high capacity, low cost batteries.

Furthermore, conventional deposition methods without using ion sources are able to deposit amorphous _LiCoO2 layers, but not crystalline _LiCoO2 layers. Surprisingly, deposition according to some embodiments of the present invention deposited _LiCoO2 layers with considerable crystallinity readily measurable by x-ray diffraction techniques. In some embodiments, the crystallinity of the as-deposited _LiCoO layer is sufficient for battery construction without further thermal treatment. In some embodiments, the crystallinity of the as-deposited _LiCoO2 layer is enhanced by thermal treatment with a low thermal budget compatible with films deposited on low temperature substrates.

Furthermore, the as-deposited stoichiometry of some _LiCoO2 layers deposited according to some embodiments of the present invention suggests that such layers are sufficient for use in batteries. With the demonstrated ability to deposit _LiCoO2 films with crystallinity and sufficient stoichiometry, cells using as-deposited _LiCoO2 films can be fabricated. Heat-treating the _LiCoO2 layer can improve the crystallinity and reduce the impedance.

In some embodiments, a _LiCoO2 crystalline layer with a <101> or <003> crystalline orientation is directly deposited on the substrate. Deposition of crystalline materials can eliminate or reduce the need for subsequent high temperature anneals or noble metal layers to crystallize and orient the film. Elimination of high-temperature annealing allows formation of battery structures on lightweight and low-temperature substrates such as stainless steel foil, copper foil, aluminum foil, and plastic sheets, thereby reducing battery weight and cost while maintaining the energy-density storage capabilities of Li-based batteries. In some embodiments, a crystalline _LiCoO2 layer can be deposited on a noble metal layer such as iridium, resulting in a further significant reduction in the ripening heat budget required to enhance crystallinity.

Material deposition by pulsed DC bias reactive ion deposition is described in the following patent application: U.S. Patent Application Serial No. 10/101863 by Hongmei Zhang et al., entitled "Biased Pulse DC Reactive Sputtering of Oxide Films", 2002 Submitted on March 16. Preparation of targets is described in the following patent application: U.S. Patent Application Serial No. 10/101,341 by Vassiliki Milonopoulou et al., entitled "Rare-Earth Pre-Alloyed PVD Targets for Dielectric Planar Applications," filed March 16, 2002. US Patent Application Serial No. 10/101,863 and US Patent Application Serial No. 10/101,341, each assigned to the same assignee as the present disclosure, are hereby incorporated in their entirety. Deposition of oxide materials is also described in US Patent No. 6,506,289, the entire contents of which are also incorporated herein by reference. Transparent oxide films can be deposited using methods similar to those described in detail in US Patent No. 6,506,289 and US Application Serial No. 10/101863.

FIG. 1A shows a schematic diagram of a reactor apparatus 10 for sputtering material from a target 12 in accordance with the present invention. In some embodiments, apparatus 10 may be, for example, an AKT-1600 PVD (substrate size of 400×500 mm) system from Applied Komatsu or an AKT-4300 (substrate size of 600×720 mm) from Applied Komatsu, Santa Clara, CA. ) system transformation. For example, the AKT-1600 reactor has three deposition chambers connected by a vacuum transfer chamber. These AKT reactors can be modified such that pulsed DC power is supplied to the target and RF power is supplied to the substrate during the deposition of the material film.

Apparatus 10 comprises a target 12 electrically connected through a filter 15 to a pulsed DC power source 14 . In some embodiments, target 12 is a target that provides a wide area sputtering source of material deposited on substrate 16 . The substrate 16 is placed parallel to and opposite to the target 12 . The target 12 functions as a cathode when power is applied thereto by a pulsed DC power supply 14 and is equivalently referred to as the cathode. Applying electrical power to target 12 generates plasma 53 . The substrate 16 is capacitively connected to the electrode 17 via the insulator 54 . The electrodes 17 may be connected to an RF power source 18 . The magnet 20 is scanned across the top of the target 12 .

For pulsed reactive dc magnetron sputtering as performed by apparatus 10, the polarity of the power supplied to target 12 by power supply 14 oscillates between negative and positive voltages. During a positive voltage, the insulating layer on the surface of the target 12 discharges and prevents arcing. To obtain arc-free deposition, the pulse frequency exceeds a critical frequency which may depend on target material, cathode current and inversion time. Using reactive pulsed DC magnetron sputtering as shown in setup 10, high quality oxide films can be prepared.

The pulsed DC power supply 14 may be any pulsed DC power supply, such as the AE Pinnacle plus 10K from AdvancedEnergy, Inc. In the case of such a DC power supply, a pulse-modulated DC power of up to 10 kW with a frequency between 0 and 350 kHz can be supplied. The reverse voltage may be negative 10% of the target voltage. Use of other power supplies may result in different power characteristics, frequency characteristics and reverse voltage percentages. The inversion time of the power supply 14 for this embodiment can be adjusted between 0 and 5 μs.

Filter 15 prevents bias power from power supply 18 from coupling into pulsed DC power supply 14 . In some embodiments, power supply 18 may be a 2 MHz RF power supply, such as the Nova-25 power supply manufactured by ENI, Colorado Springs, Co.

In some embodiments, filter 15 may be a 2 MHz sine wave band-stop filter. In some embodiments, the bandwidth of the filter may be about 100 kHz. Thus, the filter 15 prevents the 2 MHz power from the bias voltage of the substrate 16 from damaging the power supply 14 and allows the pulsed dc power and frequency to pass. .

Pulsed DC deposited films are not perfectly dense and may have a columnar structure. Columnar structures can be detrimental to thin film applications where high density is important, such as barrier films and dielectric films, due to the boundaries between the pillars. The pillars function to reduce the dielectric strength of the material, but may provide diffusion channels for the transport or diffusion of electrical currents, ionic currents, gases or other chemical agents such as water. In the case of solid-state batteries, the columnar structure with crystallinity obtained by the method according to the invention is beneficial for battery performance because the columnar structure allows better transport of Li through material boundaries.

In the Phoenix system, for example, for deposition on a surface having dimensions of approximately 600 x 720 mm, target 12 may have an effective size of approximately 800.00 x 920.00 mm x 4 to 8 mm. The temperature of the substrate 16 can be adjusted to between -50°C and 500°C. The distance between target 12 and substrate 16 may be between about 3 and about 9 cm (in some embodiments, between 4.8 and 6 cm). Process gas may be introduced into the chamber of apparatus 10 at a rate of up to 200 sccm, while the pressure in the chamber of apparatus 10 may be maintained between about 7 and 6 millitorr. Magnet 20 provides a magnetic field oriented in the plane of target 12 and having a strength between about 400 and about 600 Gauss, and moves across target 12 at a rate of less than about 20-30 seconds/scan. In some embodiments using a Phoenix reactor, the magnet 20 may be a racetrack magnet having dimensions of approximately 150mm x 800mm.

An example of target 12 is illustrated in FIG. 2 . The film deposited on the substrate on the carrier plate 17 facing the region 52 of the target 12 has good thickness uniformity. Region 52 is the region shown in FIG. 1B that is exposed to a uniform plasma environment. In some implementations, carrier 17 may be coextensive with region 52 . Region 24 shown in FIG. 2 refers to a region within which physically and chemically uniform deposition can be achieved simultaneously, for example, where physical and chemical uniformity provides refractive index uniformity, oxide film uniformity, or metal film uniformity. Figure 2 shows a region 52 of the target 12 that provides thickness uniformity that is generally larger than region 24 of the target 12 that provides thickness and chemical uniformity to the deposited film. However, in a preferred approach, regions 52 and 24 may be coextensive.

In some embodiments, magnet 20 extends beyond region 52 in one direction, such as the Y direction in FIG. 2 , so that scanning is only necessary in one direction, such as the X direction, to provide a time-averaged uniform magnetic field. As shown in FIGS. 1A and 1B , magnet 20 may scan across the entire extent of target 12 that is larger than uniform sputter-eroded region 52 . The magnet 20 moves in a plane parallel to the plane of the target 12 .

The combination of a uniform target 12 and a target region 52 that is larger than the substrate region 16 can provide a film of highly uniform thickness. In addition, the material properties of the deposited film can be highly uniform. The sputtering conditions of the target surface, such as the uniformity of erosion, the average temperature of the plasma at the target surface, and the equilibrium of the target surface with the gas phase environment of the process, are uniform over an area greater than or equal to the area coated with a uniform film thickness. Additionally, the area of uniform film thickness is greater than or equal to the area of a film with highly uniform electrical, mechanical, or optical properties such as refractive index, stoichiometry, density, transmission, or absorptivity.

Target 12 may be formed from any material that provides the proper stoichiometry for _LiCoO2 deposition. Typical ceramic target materials comprise oxides of Li and Co as well as metallic Li and Co additives and dopants such as Ni, Si, Nb or other suitable metal oxide additives. In the present disclosure, the target 12 may be formed of LiCoO ₂ for depositing a LiCoO ₂ film.

In some embodiments of the invention, bricks of material are formed. These bricks may be assembled on a backing plate to form a target for device 10 . Wide area sputter cathode targets can be formed from dense arrays of smaller bricks. Thus, the target 12 may comprise a plurality of bricks, for example between 2 and 60 individual bricks. The tiles may be finished to a size that provides an edge-to-edge non-contact tile-to-tile width of less than about 0.010" to about 0.020" or less than half a millimeter to eliminate friction that may occur between adjacent tiles of tile 30. plasma treatment. In FIG. 1B , the distance between the brick of target 12 and the dark space anode or ground shield 19 can sometimes be greater to provide a non-contact assembly or to provide thermal expansion tolerance during chamber adjustment or operation.

As shown in FIG. 1B , in the region overlying the substrate 16 , a uniform plasma environment can be created in the region between the target 12 and the substrate 16 . A plasma 53 may be generated in a region 51 extending below the entire target 12 . Central region 52 of target 12 may be subject to uniform sputter erosion conditions. As discussed further herein, layers deposited on the substrate anywhere beneath central region 52 may then be uniform in thickness and other properties (ie, dielectric, optical index, or material concentration). In some embodiments, target 12 is substantially flat to provide uniformity of the film deposited on substrate 16 . In practice, the planarity of target 12 may mean that all portions of the target surface in region 52 are flat surfaces of no more than a few millimeters, and may typically be no more than 0.5 mm flat.

Figure 3 shows a cell structure with a _LiCoO2 layer deposited according to some embodiments of the present invention. As shown in FIG. 3 , a metal collector layer 302 is deposited on a substrate 301 . In some embodiments, the collector layer 302 can be patterned in various ways prior to depositing the LiCoO ₂ layer 303 . Also, according to some embodiments, the LiCoO ₂ layer 303 may be a deposited crystalline layer. In some embodiments of the invention, layer 303 is already crystallized without heat treatment for crystallization. Thus, the substrate 301 may be a silicon wafer, titanium metal, alumina or other conventional high temperature substrates, but may also be a low temperature material such as plastic, glass or other materials that can be sensitive to damage from high temperature crystallization heat treatments. This characteristic can have the great advantage of reducing the cost and weight of battery structures formed by the present invention. The low-temperature deposition of _LiCoO2 allows the continuous deposition of battery layers one after the other. This approach has the advantage of obtaining continuous battery structural layers in a laminated state without the inclusion of a substrate layer. Laminated cells offer higher specific energy density and low impedance charging and discharging operations.

In some embodiments, an oxide layer may be deposited on substrate 301 . For example, a silicon oxide layer can be deposited on a silicon wafer. Other layers may be formed between the conductive layer 302 and the substrate 301 .

As further shown in FIG. 3 , a LiPON layer 304 (Li _x PO _y N _z ) is deposited on top of the LiCoO ₂ layer 303 . The LiPON layer 304 is the electrolyte of the battery 300, while the _LiCoO2 layer 303 acts as the cathode. A metal conductive layer 305 can be deposited over the LiPON layer 304 to complete the cell. The metal conductive layer 305 may contain lithium adjacent to the LiPON layer 304 .

On top of the LiPON layer 304 is deposited an anode 305 . Anode 305 may be, for example, evaporated lithium metal. Other materials such as nickel may also be used. A collector electrode 306 , which is a conductive material, is then deposited over at least a portion of the anode 305 .

The Li-based thin film battery operates by Li ions migrating in a direction from the collector electrode 306 to the collector electrode 302 to maintain the voltage between the collector electrode 306 and the collector electrode 302 at a constant voltage. Thus, the ability of the battery structure 300 to supply a stable current depends on the ability of Li ions to diffuse through the LiPON layer 304 and the LiCoO ₂ layer 303 . Li migration through the bulk cathode _LiCoO2 layer 303 in thin film cells occurs via grains or grain boundaries. Without being bound by any particular migration theory in this disclosure, it is believed that the grains whose planes are parallel to the substrate 302 block the flow of Li ions while being oriented in a plane perpendicular to the substrate 301 (i.e., aligned with the Li ions). Oriented parallel to the direction of ion flow) facilitates Li diffusion. Therefore, in order to provide a high current battery structure, the _LiCoO2 layer 303 should contain crystals oriented in the <101> direction or the <003> direction.

According to the present invention, a _LiCoO2 film can be deposited on the substrate 302 using a pulsed DC biased PVD system as described above. Alternatively, the AKT 1600 PVD system can be modified to provide RF bias and an Advanced Energy Pinnacle plus 10K pulsed DC power supply can be used to power the target. The pulse frequency of the power supply can vary from about 0 KHz to about 350 KHz. The power output of the power supply is between 0 and about 10 kW. In the case of dc sputtering, a target of dense _LiCoO2 bricks with a resistivity in the range of about 3 to about 10 kΩ can be used.

In some embodiments, _LiCoO2 films are deposited on Si wafers. A gas flow comprising oxygen and argon may be used, and in some embodiments the ratio of oxygen to argon ranges from 0 to about 50% with a total gas flow of about 80 seem. During deposition, the pulse frequency ranges from about 200 kHz to about 300 kHz. An RF bias can also be applied to the substrate. In multiple experiments, the deposition rate varied from about 2??/(kW sec) to about 1???/(kW sec) depending on the _O2 /Ar ratio and substrate bias.

Table I illustrates some exemplary depositions of _LiCoO2 according to the present invention. XRD (x-ray diffraction) results taken on the resulting films indicate that the films deposited according to the present invention are crystalline films, typically with highly textured grain sizes up to about 150 nm. The dominant crystal orientation appears to be sensitive to the O ₂ /Ar ratio. For certain _O2 /Ar ratios (-10%), the as-deposited films have preferred orientations in the <101> direction or <003> direction and poorly grown <003> planes.

Figures 4A and 4B illustrate the XRD analysis and SEM cross-section, respectively, of the _LiCoO2 film deposited as Example 15 in Table I. This _LiCoO2 film was deposited on a Si wafer using a target power of 2kW, a frequency of 300kHz, and 60sccm of Ar and 20sccm of _O2 for a substrate with an initial temperature of approximately 30°C. As shown in the XRD analysis of Fig. 4A, the strong <101> peak indicates that the strong orientation of _LiCoO2 crystals is displayed in the proper <101> crystallographic direction. The SEM cross-section shown in Fig. 4B further reveals the columnar structure of the film with <101> orientation and the grain boundaries of the resulting _LiCoO2 crystals.

5A to 5E show SEM cross-sections of further exemplary deposited _LiCoO crystals according to the present invention. In each example, deposition of _LiCoO2 films was performed on Si wafers using a target power of about 2 kW and a frequency of about 250 kHz. The _LiCoO2 film shown in Figure 5A corresponds to the exemplary deposition Example 1 in Table I. In the deposition of the _LiCoO2 film shown in FIG. 5A, no bias power was used, and the argon gas flow rate was about 80 sccm and the oxygen gas flow rate was about 0 sccm. A deposition rate of about 1.45 μm/hour was achieved over the entire substrate area of 400×500 mm. Furthermore, as illustrated in the cross-section shown in Fig. 5A, the <101> orientation of _LiCoO2 is achieved.

The deposition rate of the _LiCoO2 layer shown in Figure 5A is high, possibly attributed to the higher conductivity or lower resistivity of the ceramic _LiCoO2 oxide sputtering target. Using an ohmmeter, a target resistance of 10 kiloohms was measured over a distance of about 4 cm on the surface of the target 12 . This high rate can produce LiCoO2 layers equal to or thicker than 3 micrometers required for batteries at a high rate over a wide area and in a short time, resulting in high productivity and low cost. At such low target powers, target resistances of the order of 500 kΩ or higher measured by the same measurement technique over the same distance do not allow such high sputtering efficiencies or high deposition rates. The electrical resistance of conventional target materials may be unmeasurably high. A resistance of 100 kΩ over a surface of about 4 cm results in high sputtering efficiency and high deposition efficiency. Furthermore, since the deposition rate is typically almost linearly proportional to the target power, deposition at 6 kW yields a deposition rate of about 3 μm/hour, which is a reasonable amount for a Li-based thin-film solid-state battery over a surface area of 400 × 500 ^mm2 . Manufacturability is a very favorable deposition rate.

The _LiCoO2 layer shown in Figure 5B was deposited under the conditions listed as Example 7 in Table I. Also, no bias voltage was used in the deposition. An argon flow of about 72 seem and an oxygen flow of about 8 seem was used. The deposition rate is significantly reduced to about 0.85 μm/hour. Furthermore, although <101> crystallization could be discerned, <101> crystallization was not evident in the deposition of the film shown in Figure 5A.

The _LiCoO2 films shown in Figure 5C were deposited according to Example 3 in Table I. In this deposition, a bias power of 100 W was applied to the substrate. In addition, an argon flow of 72 seem and an oxygen flow of 8 seem were used. The deposition rate was about 0.67 μm/hour. Therefore, the application of the _bias voltage further reduces the deposition rate (from 0.85 μm/hour for the example shown in FIG. 5B to 0.67 μm/hour for the example shown in FIG. μm/hour). Furthermore, the required <101> directionality of the formed crystals appears to be further reduced.

The _LiCoO2 film shown in Fig. 5D corresponds to Example 4 in Table I. In this deposition, the Ar/ _O2 ratio is increased. As shown in Figure 5D, increasing the ratio of Ar/ _O2 improves crystallinity. Relative to the embodiment illustrated in FIG. 5C, the deposition illustrated in FIG. 5D was performed using an argon flow of about 76 seem and an oxygen flow of about 4 seem and maintaining a bias voltage of 100 W to the substrate. The deposition rate of _LiCoO2 increased from the rate of 0.67 μm/hour illustrated in Figure 5C to 0.79 μm/hour.

The exemplary deposition illustrated in Figure 5E corresponds to Example 5 in Table I. The substrate temperature was set at about 200°C while maintaining the bias power at about 100W. The argon flow was set at about 76 seem, and the oxygen flow was set at about 4 seem. The deposition rate of the resulting _LiCoO2 layer is about 0.74 μm/hour.

In Example 6 of Table I, the argon flow was set at about 74 seem and the oxygen flow was set at about 6 seem, resulting in a _LiCoO2 deposition rate of about 0.67 μm/hour. Thus, increasing both the argon and oxygen flow rates resulted in lower deposition rates relative to the deposition illustrated in Figure 5E.

The data clearly show that as-deposited _LiCoO2 crystalline films can be obtained under several process operating conditions as shown in Table II. In particular, for the process operating conditions according to embodiments of the present invention, a very high deposition rate at low power is obtained and at the same time an oriented crystal structure is obtained.

Figure 6A illustrates a _LiCoO2 layer 602 deposited on a thin substrate 601 according to some embodiments of the invention. Higher Li-ion mobility can be achieved using a crystalline _LiCoO2 cathode film 602 deposited on a thin substrate 601 having a thickness comparable to that of the battery stack itself, rather than having the battery stack Multiple or dozens of times the thickness of the This film can lead to faster charge and discharge rates. Substrate 601 may be formed from a thin sheet of metal such as aluminum, titanium, stainless steel, or other suitable thin sheet of metal, may be formed from a polymer or plastic material, or may be formed from a ceramic or glass material. As shown in Figure 6B, if the substrate 601 is an insulating material, a conductive layer 603 can be deposited between the substrate 601 and the _LiCoO2 layer 602.

Depositing material on thin substrates involves holding and positioning the substrate during deposition. 7A, 7B, 7C and 7D illustrate a reusable fixture 700 for holding thin film substrates. As shown in FIG. 7A, a reusable fixture 700 includes a top 701 and a bottom 702 that snap together. A thin substrate 601 is placed between the top 701 and the bottom 702 . As shown in FIG. 7B , top 701 and bottom 702 cause substrate 601 to be tensioned and then clamped as top 701 approaches bottom 702 . The substrate 601 can be easily fixed by the fixing device 700 so that the substrate 601 can be handled and positioned. In some embodiments, the corners or regions 703 of the substrate 601 are removed so that the substrate 601 can be stretched more easily as the top 701 approaches the bottom 702 by avoiding the "wrap around" corner pinching.

As shown in FIG. 7C , a mask 712 may be attached to fixture 700 . In some implementations, the fixture 700 includes guides to align the fixture 700 with the mask 712 . In some embodiments, mask 712 may be attached to fixture 700 and move with fixture 700 . Mask 712 may be placed at any suitable height on substrate 601 in fixture 700 . Thus, mask 712 may function as a contact or proximity mask. In some embodiments, mask 712 is formed from another thin substrate that fits in a fixture similar to fixture 700 .

As shown in FIGS. 7C and 7D , fixture 700 and mask 712 may be placed relative to support 710 . For example, support 710 may be a pedestal, support or electrostatic chuck of a processing chamber as shown in FIGS. 1A and 1B . Fixture 700 and mask 712 may have structural elements that allow for easy alignment with each other and with support 710 . In some embodiments, mask 712 is inherent in the processing chamber, and as shown in FIG. 7D , and is aligned with fixture 700 during positioning of fixture 700 on support 710 .

Using a fixture 700 as shown in Figures 7A, 7B, 7C and 7D allows processing of thin film substrates in a processing chamber. In some embodiments, the thin film substrate can be approximately 10 μm or larger. Furthermore, once assembled in fixture 700, thin film substrate 601 may be processed and moved from processing chamber to processing chamber. Thus, multi-chamber systems can be used to form stacks comprising one or more _LiCoO2 layers deposited according to embodiments of the present invention.

FIG. 8 illustrates a cluster-type apparatus 800 for processing thin film substrates. For example, the cluster-type facility 800 may include a load lock 802 and a load lock 803 by which the assembled thin film substrate 601 is loaded and the resulting device is taken out of the cluster-type facility 800 . Chambers 804, 805, 806, 807, and 808 are processing chambers for deposition, heat treatment, etching, or other processing of materials. One or more of chambers 804, 805, 806, 807, and 808 may be pulsed DC PVD chambers as described above with respect to FIGS. ₂ films.

Process chambers 804 , 805 , 806 , 807 and 808 and load locks 802 and 803 are connected by transfer chamber 801 . Transfer chamber 801 includes a substrate transfer robot that moves individual wafers back and forth between process chambers 804 , 805 , 806 , 807 , and 808 and load locks 802 and 803 .

In conventional thin film battery fabrication, a ceramic substrate is loaded into a load lock 803 . A thin metal layer may be deposited in chamber 804 followed by LiCoO ₂ deposition in chamber 805 . The substrate is then removed through the load lock 803 for heat treatment in the air outside the cluster tool 800 . The processed wafers are then reloaded into the cluster tool 800 via the load lock 802 . A LiPON layer may be deposited in chamber 806 . The wafer is then removed again from the cluster tool 800 to deposit the lithium anode layer, or chamber 807 may sometimes be modified to deposit the lithium anode layer. A second metal layer is deposited in chamber 808 to form the charge and anode collectors. The completed battery structure is then unloaded from the aggregated facility 800 through the load lock 802 . Wafers are moved back and forth between chambers by robotic arms in the transfer chamber 801 .

Battery structures fabricated in accordance with the present invention may use thin film substrates loaded into fixtures such as fixture 700 . The fixture 700 is then loaded into the load lock 803 . Chamber 804 may also include the deposition of a conductive layer. Chamber 805 then includes the deposition of a _LiCoO2 layer according to an embodiment of the invention. A LiPON layer may then be deposited in chamber 806 . Chamber 807 can also be adapted to deposit lithium-rich materials such as lithium metal, and chamber 808 can be used to deposit the conductive layer of the collector. In this method, no heat treatment was used to crystallize the _LiCoO2 layer.

Another advantage of the thin film battery process is the ability to stack battery structures. In other words, substrates loaded into cluster tool 800 may pass through processing chambers 804, 805, 806, 807, and 808 multiple times to fabricate multiple stacked battery structures. 9A and 9B illustrate these battery structures.

Figure 9A shows a parallel bonded stack. As shown in FIG. 9A , a substrate 601 , which may be a plastic substrate, for example, is loaded into a load lock 803 . Conductive layer 603, such as aluminum, copper, iridium or other materials of about 2 μm, serves as the bottom collector. For example, conductive layer 603 may be deposited in chamber 804 . A LiCoO ₂ layer 602 is then deposited on the conductive layer 603 . According to an embodiment of the present invention, the LiCoO ₂ layer 602 may be about 3-10 μm and may be deposited in chamber 805 . The wafer can then be moved into chamber 806 where a LiPON layer 901 can be deposited to a thickness of about .5 to about 2 μm. In chamber 807, an anode layer 902, eg, up to about 10 μm of lithium metal, may then be deposited therein. A second conductive layer 903 is then deposited over the anode layer 902 . A second battery stack formed of metal layer 603 , LiCoO ₂ layer 602 , LiPON layer 901 , lithium layer 902 and current collecting conductive layer 903 may then be deposited on top of the first battery stack. On top of the current collecting conductive layer 903, another lithium layer 902 is formed. Another LiPON layer 901 is formed on top of the lithium layer 902 . Another LiCoO ₂ layer 602 is formed on top of the LiPON layer 901 , and finally another metal layer 603 is formed on top of the LiCoO ₂ layer 602 . In some embodiments, additional laminates may be formed. In some embodiments, metal layers 603 and 903 differ in the mask used for deposition to form small protrusions for electrically connecting the layers.

As noted above, any number of individual battery stacks can be formed to form a parallel battery structure. The parallel configuration of this battery stack structure can be expressed as: collector/LiCoO ₂ /LiPON/anode/collector/anode/LiPON/LiCoO ₂ /collector/LiCoO ₂ . . . /collector. Figure 9B shows an alternative stack for the corresponding cell structure: collector/ _LiCoO2 /LiPON/anode/collector/LiCoO2/ _LiPON /anode/collector.../collector. In this case, since the respective battery stacks share the anode, a battery stack structure arranged in series is formed.

To form the structures shown in Figures 9A and 9B, the substrate is again rotated through the chamber of the cluster tool 800 to deposit sets of cells. In general, stacks of any number of cells can be formed in this manner.

In some embodiments, stoichiometric _LiCoO2 can be deposited on iridium. Figures 10A to 10D illustrate the annealing process used to deposit Li-Co over an iridium layer that has been deposited on a Si wafer. LiCoO was done at target power of 2 kW, no bias power, inversion time of 1.6 μs, pulse frequency of 300 kHz, Ar flow of 60 sccm and O _flow of 20 sccm, without pretreatment, for 7200 s ₂ deposition. As a result, a _LiCoO2 layer of about 1.51 μm was deposited.

Figures 10A to 10D show the XRD analysis of the as-deposited and annealed layers of LiCoO _deposited as described above. XRD analysis of the as-deposited layer confirmed a weak peak at _2θ = 18.85° indicative of the <003> orientation of crystalline LiCoO, a sharper peak at about 20 = 38.07° consistent with the desired <101> The <111> direction corresponds to the peak at 2θ=40.57°. However, the position of the <101> LiCoO ₂ peak indicates that the <101> LiCoO ₂ peak is non-stoichiometric LiCoO ₂ . To be beneficial for use as a battery layer, stoichiometric _LiCoO2 provides the best Li transport. Those of ordinary skill in the art will note that careful adjustment of the deposition parameters can provide stoichiometric _LiCoO2 in the proper orientation.

Figure 10B shows the XRD analysis of the sample shown in Figure 10A after annealing in air at 300°C for 2 hours. As shown in FIG. 10B , the XRD peak corresponding to <003> LiCoO ₂ is enhanced, indicating LiCoO ₂ crystallization into the <003> direction. In addition, the <101> peak of LiCoO ₂ is slightly shifted to 2θ = 38.53°, indicating a more stoichiometric crystallization of <101> LiCoO ₂ . However, after such annealing, crystalline _LiCoO is still not stoichiometric. One of ordinary skill in the art should note that with annealing temperatures equal to or less than 300 °C, longer annealing and/or further adjustment of the deposited stoichiometry can lead to usefully oriented _{stoichiometric} LiCoO layers. Therefore, low temperature materials such as polymers, glass or metals can be used as substrates.

Figure 10C illustrates the XRD analysis from the sample after 2 hours of subsequent 500°C annealing in air. As shown in Figure 10C, more _LiCoO2 crystallized into the <003> layer. Furthermore, the <101> _LiCoO2 peak shifted again to 20 = 39.08°, indicating the crystallization of the <012> layer of _LiCoO2 . In this case, the <012> _LiCoO2 crystals are stoichiometric, thus allowing efficient Li migration. Those of ordinary skill in the art should note that in the case of annealing temperatures equal to or less than 500 °C, longer annealing and/or further adjustment of the deposited stoichiometry can lead to usefully oriented stoichiometric _LiCoO2 layers. Therefore, low temperature materials such as polymers, glass or metals can be used as substrates.

Figure 10D illustrates the XRD analysis of the sample after a 2 hour subsequent 700°C anneal in air. As shown in FIG. 10D , the <003> LiCoO ₂ peak disappeared, but the <012> LiCoO ₂ peak remained relatively the same as that shown for the 500° anneal illustrated in FIG. 10C .

Figures 10A to 10D demonstrate the low temperature deposition of <101> LiCoO ₂ on top of an iridium layer. A subsequent 500°C anneal may be appropriate to alter the stoichiometry of the <101> _LiCoO layer, but a 700°C anneal appears unnecessary. The deposition of a _LiCoO layer on a conductive iridium layer can be achieved on glass, aluminum foil, plastic, or other low-temperature substrate materials at an annealing temperature less than 500°C. Annealing temperatures less than 500 °C but greater than 300 °C or prolonging the low temperature annealing time can also lead to the desired orientation of stoichiometric crystalline _LiCoO2 .

11A-11D illustrate the formation of single layer cells according to some embodiments of the invention. As shown in FIG. 11A , a lift-off layer 1102 may be deposited on a substrate 1101 . Additionally, an iridium layer 1103 may be deposited over the lift-off layer 1102 . In some embodiments, the substrate 1101 can be plastic, glass, Al foil, Si wafer, or any other material. Release layer 1102 may be any release layer and may be a polymer layer such as polyimide, an inorganic layer such as _CaF2 or carbon, or an adhesive layer that loses its adhesion due to, for example, oxidation, heat or light. Release layers are well known. The iridium layer 1103 can be about or thicker.

As shown in FIG. 11B , a layer of LiCoO ₂ is deposited on top of the iridium layer 1103 as described above. In some embodiments, annealing may be performed at this step. In some embodiments, additional battery layers may be deposited prior to performing the annealing step. In some embodiments, a stoichiometric _LiCoO2 layer of useful crystallographic orientation can result in as-deposited _LiCoO2 without further annealing.

11C illustrates the deposition of a LiPON layer 1105 over the _LiCoO2 layer, the deposition of a Li layer 1106 over the LiPON layer 1105, and the deposition of an electrode layer 1107 over the Li layer 1106. In some embodiments, an annealing step up to 500° C. as described above may be performed here.

As shown in FIG. 11D , the resulting individual layer cell consisting of an iridium layer 1103, a _LiCoO2 layer 1104, a LiPON layer 1105, a Li layer 1106, and an electrode layer 1107 can be "peeled off" from a substrate 1101. form. Such individual layer cells can be self-supporting cells with a thickness of about 5 μm or more. Without the need for the substrate 1101, such batteries are known to have energy storage capabilities of greater than about 1 kW-hour/liter.

As an alternative to the lift-off method as described in FIGS. 11A to 11D , the substrate can be removed during annealing, leaving individual layer cells. Additionally, in some embodiments, substrate 1101 may be removed using solvents, etching, or photoprocessing. Furthermore, individual layer cells may be combined or stacked in any manner to provide a device with greater energy storage at a particular voltage.

Figure 12A illustrates the XRD analysis of _an as-deposited _LiCoO2 film (Example 32 in Table I) on an _Al2O3 substrate. A broad <003> crystalline _LiCoO2 peak is observed. The remaining peaks in the analysis (not labeled in Figure 12A) arise from _{the Al2O3} substrate. The <003> peak is characteristic of the layered structure in the as-deposited crystalline _LiCoO2 film according to an embodiment of the present invention.

Figure 12B illustrates the crystallinity of the _LiCoO2 film shown in Figure 12A after annealing at 700°C for 2 hours. As shown in Figure 12B, the <003> peak became sharper and higher, indicating better crystallinity. As shown in FIGS. 12G to 12J , compared with 12C to 12F , the columnar structure matures with annealing, and the grain size becomes larger with annealing. Figure 12B also shows the <012> and <006> crystalline peaks.

Figures 12C to 12F show SEM photographs of the grain size of the as-deposited film corresponding to Example 32 in Figure 1 . Figures 12G to 12J show SEM photographs of the grain size of the annealed film as illustrated in Figure 12B. A comparison of Figures 12C-12F with Figures 12G-12J illustrates that the annealing treatment produces increased grain size.

Figure 12K illustrates a fractured cross-sectional SEM of the morphology of the as-deposited crystalline film corresponding to Example 31 in Table I. Figure 12L illustrates a similar cross-sectional SEM of a film grown according to Example 32 in Table I.

Those skilled in the art will recognize variations and modifications of the embodiments specifically discussed in this disclosure. Such changes and modifications are intended to be within the scope and spirit of the present disclosure. Likewise, the scope is limited only by the appended claims.

Table II

Claims (24)

1. one kind deposits LiCoO ₂The method of layer, described method comprises:

Substrate is placed in the reactor;

Make the admixture of gas that comprises argon gas and oxygen flow through described reactor; With

With pulse modulated DC power impose on that described relatively substrate places by LiCoO ₂The target that forms,

Wherein on described substrate, deposit LiCoO ₂Crystallizing layer.

2. the described method of claim 1, described method also comprise the RF bias voltage are imposed on described substrate.

3. the described method of claim 1, wherein said crystallizing layer be＜101〉orientation.

4. the described method of claim 1, wherein said crystallizing layer be＜003〉orientation.

5. the described method of claim 1, the grain size of wherein said crystallizing layer exists

Extremely

Between.

6. the described method of claim 1, wherein said substrate is the material that is selected from the group of being made up of silicon, polymer, glass, pottery and metal.

7. the described method of claim 1, described method also comprise and described substrate are preheated to 200 ℃ temperature.

8. the described method of claim 1, wherein said substrate is a low-temperature substrate.

9. the described method of claim 8, wherein said low-temperature substrate are one that comprises in the group of substrate of glass, plastics and metal forming.

10. the described method of claim 1 also is included in deposited oxide layer on the described substrate.

11. the described method of claim 10, wherein said oxide skin(coating) is a silicon dioxide layer.

12. the described method of claim 3, wherein said crystallizing layer are with greater than 1 μ m/ hour deposited at rates.

13. the described method of claim 1, wherein said target are across the resistance of the surface measurement of the 4cm ceramic LiCoO less than 500k Ω ₂Sputtering target.

14. the described method of claim 1 also is included in depositing metal layers on the described substrate.

15. the described method of claim 14, wherein said metal level is an iridium.

16. the described method of claim 14 also comprises described LiCoO ₂Layer is at the annealing temperature that is less than or equal to 500 ℃.

17. the described method of claim 14 also comprises described LiCoO ₂Layer is at the annealing temperature that is less than or equal to 400 ℃.

18. a method of making battery, described method comprises:

Substrate is loaded in the accumulation type equipment;

With conductive layer deposition on described substrate, and use pulse modulated direct current physical gas-phase deposite method in the chamber of described accumulation type equipment with crystallization LiCoO ₂Be deposited upon on the described conductive layer.

19. the described method of claim 18, wherein depositing crystalline LiCoO ₂Layer comprises and passes mask depositing crystalline LiCoO ₂

20. the described method of claim 18 also is included in described LiCoO ₂Deposition LiPON layer above the layer.

21. the described method of claim 20 also is included in deposition anode above the described LiPON layer.

22. the described method of claim 21 also is included in depositing conducting layer above the described anode.

23. the described method of claim 18, wherein said conductive layer are the iridium layers.

24. the described method of claim 18 also comprises battery structure is peeled off from described substrate.

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